1. Field of the Invention
The invention pertains to an x-ray examination apparatus that includes a carrier supporting an x-ray source for generating an x-ray beam, an x-ray detector facing the x-ray source, and a film holder, the film holder being displaceable between an exposure position in front of the x-ray detector and a standby position outside the x-ray beam path.
2. Description of the Related Art
An x-ray examination apparatus having the possibility of optionally employing either an x-ray detector, notably an x-ray image intensifier, or a film holder has been described in U.S. Pat. No. 4,879,736.
In U.S. Pat. No. 4,879,736 the film holder is pivotable from a standby position to an exposure position, the film holder remaining attached to the image intensifier. The film holder is mounted on a bearing surrounding the image intensifier, so that it can be displaced between various standby positions around the image intensifier. The apparatus described in the cited Patent Specification is not balanced. Consequently, a powerful system of motors and brakes is needed for displacing the film holder between its standby and exposure positions and for moving the carrier; therefore the carrier having the form of a C-shaped support cannot be moved manually without considerable effort.
It is inter alia an object of the invention to provide an x-ray examination apparatus in which alternatively an x-ray detector or a film holder can be used, such that the film holder neither obscures, nor impedes access to the patient when not in use.
To achieve this, an x-ray examination apparatus in accordance with the invention is characterised in that the film holder is mounted movably on a frame which itself is movably connected to the carrier, the film holder with the frame being displaceable between a park position against an inner circumference of the carrier and a standby position next to the x-ray detector, and the film holder being displaceable between the standby position and an exposure position located in front of the x-ray detector.
The film holder can by choice be positioned either in a park position where the frame is positioned against an inner circumference of the carrier, or in a standby position, in which the film holder is positioned next to the x-ray detector, notably an x-ray image intensifier, and an input screen of the image intensifier and an image recording plane in the film holder are preferably situated substantially in a common plane perpendicular to the central ray, or the film holder an be positioned in an exposure position in which it is orthogonal to a central ray and the image recording plane in the film holder is situated at a distance to the x-ray source which is equal to the distance between the x-ray detector to the x-ray source when the film holder is in its standby position.
Because in its park position the film holder and the frame supporting it are positioned against the inner circumference of the carrier and near a suspension of the carrier from its vertical support, it is achieved that the patient region is vacated by the film holder and that, moreover, vision and access to the patient (region) are not impeded by the film holder when it is not being used. Furthermore, the film holder in its park position does not protrude beyond an outer circumference of the carrier, so that even in its park position the film holder does not restrict the motion of the carrier.
The frame supporting the film holder is mounted pivotably about an axis perpendicular to the plane of the carrier. The film holder can be moved to its standby position by rotation of the frame around this axis. In this standby position the film holder is next to the image intensifier and in the same plane as the input screen of the image intensifier. In this standby position, the film holder is approximately level with the connection of the carrier to its vertical stand. In this position the film holder is situated next to the patient region and preferably so high above the floor that it is conveniently reached by a person standing next to the x-ray examination apparatus. Consequently, in the standby position the film holder can be conveniently prepared for exposure, i.e. installing or removing film cassettes, positioning the patient or collimating the x-ray beam, without disturbance to the patient or life support systems.
The film holder is mounted pivotably on the frame such that it can be rotated about an axis orthogonal to the frame so as to reach the exposure position. In the exposure position the film holder and the x-ray detector have a common image axis, so that x-radiation transmitted through the film holder can be employed, using the x-ray detector, to monitor the image formed on the film.
It is to be noted that the balancing of the motion of the film holder by means of a counterweight which moves in the opposite direction is known per se from U.S. Pat. No. 4,358,856.